The present invention relates to a combination speed limiter and transmission interlock system, and more particularly to a combination speed limiter and transmission interlock system for engine-transmission power trains such as outboard motors.
Conventional outboard motors typically comprise a speed limiter module and a transmission interlock module. These modules are separate from each other. Each module requires its own external connections, components, housing, and manufacturing.
One disadvantage of the foregoing separate modules is that they require numerous connections external to the modules. Some of the connections are duplicated from module to module. For example, both the speed limiter module and the transmission interlock module typically require a connection to a coil of the ignition system of the engine and a connection to ground. The transmission interlock module also typically requires two connections to a switch interconnected to the transmission. A large number of connections increases the likelihood of a failure. If any of these connections is broken, either deliberately or by accident, the effectiveness of the representative individual module may be lost.
Another disadvantage of the foregoing separate modules is that they require a separate housing for each module. Two separate housings necessitate additional tooling, manufacturing time, space in the outboard motor housing, components, and connections. On outboard motors and the like, space considerations are a concern.
A combination speed limiter and transmission interlock system for an outboard motor and/or other engine-transmission power train (e.g., a lawnmower) is disclosed which is inexpensive, expected to be more reliable, and which may be retrofit on and/or made an option of an existing and/or new outboard motor and/or other engine-transmission power train. The combination speed limiter and transmission interlock system is preferably used with an engine-transmission power train including an engine having a fixed-timing ignition system and a transmission interconnected to a transmission switch. The ignition system may include a coil that generates an ignition pulse that is utilized to cause an igniter to ignite an air-fuel mixture, thereby resulting in a combustion event. The transmission switch may indicate when the transmission is in a neutral position and when the transmission is in an in-gear position.
The combination speed limiter and transmission interlock system of the invention is preferably located in a single module having a housing. The module includes circuitry that performs both speed limiter and transmission interlock functions. The speed limiter portion limits the output of the engine when a limit speed is reached. The transmission interlock portion prevents the engine from starting when the transmission is not in neutral.
The circuitry is electrically coupled to the coil, ground (e.g., metal chassis or frame) and the transmission switch via electrical conduits (e.g., leads or wires) that extend external of the housing. The circuitry includes an ignition control circuit that prevents the igniter from igniting the air-fuel mixture to cause a combustion event, a speed control circuit that causes the ignition control circuit to prevent the igniter from igniting the air-fuel mixture when the engine exceeds a limit speed, and a start control circuit that causes the ignition control circuit to prevent the igniter from igniting the air-fuel mixture when the transmission switch indicates the in-gear position of the transmission during starting of the engine. The circuitry may also include an inhibitor control circuit that prevents the start control circuit from causing the ignition control circuit to prevent the igniter from igniting the air-fuel mixture when the transmission switch indicates the in-gear position of the transmission during running of the engine.
In one embodiment, the invention provides an analog version of the combination speed limiter and transmission interlock system. The ignition control circuit includes a switch that is responsive to signals received from the speed control circuit and the start control circuit. The speed control circuit includes a speed circuit and an electrical storage device for receiving electrical energy that is associated with the ignition pulse. In one embodiment, the electrical storage device receives the electrical energy during the leading half-cycle of the ignition pulse, although the center half-cycle or the trailing half-cycle of the ignition pulse could be used. The voltage of the electrical energy received by the electrical storage device is limited by the speed circuit. The speed circuit receives the electrical energy discharged from the electrical storage device, and generates a signal based on the electrical energy received. If the received electrical energy is above a minimum voltage value at the time a combustion event is suppose to occur, the signal acts as a trigger that turns ON the switch of the ignition control circuit, thereby limiting the voltage of the ignition pulse to a value too low to cause the igniter to ignite.
When the transmission switch is the in-gear position during engine starting, the start control circuit turns ON the switch of the ignition control circuit. When the transmission switch is in the neutral position during engine starting, the switch remains in the OFF position. After proper engine startup, upon reaching a minimum engine speed, the inhibitor circuit inhibits the start control circuit from turning ON the switch, thereby allowing the operator to shift the transmission out of neutral for operation of the power train.
In another embodiment, the invention provides a digital version of the combination speed limiter and transmission interlock system. The digital system includes a programmable device. The programmable device utilizes a software program having a plurality of instructions, and interprets and executes the software instructions to control the outboard motor and/or other engine-transmission power train. The speed limiter of the digital system is configured to limit the output of the engine when a limit speed is reached. The transmission interlock of the digital system is configured to prevent the engine from starting when the transmission is not in neutral. The software program includes instructions corresponding to speed limiter and transmission interlock functions. In one embodiment, analog components associated with the programmable device provide inputs to the programmable device including a signal corresponding to the speed of the engine and a signal corresponding to the position of the transmission (e.g., in neutral or in gear). Based on the inputs, the programmable device determines a limit condition (i.e., whether or not the voltage of the ignition pulse needs to be limited). The programmable device provides an output corresponding to the limit condition to the ignition control circuit. If the programmable device determines the voltage of the ignition pulse needs to be limited, the output corresponding to the limit condition causes a switch to be turned ON, thereby limiting the voltage of the ignition pulse. If the programmable device determines the voltage of the ignition pulse does not need to be limited, the output corresponding to the limit condition causes the switch to be turned OFF, thereby allowing the voltage of the ignition pulse to be utilized to ignite the igniter. In one embodiment, the voltage of the ignition pulse is limited to a value below that which is necessary to ignite the igniter. The voltage of the ignition pulse is limited, for example, if the engine has reached a limit speed and/or if the transmission is not in neutral when the operator attempts to start the engine.
The digital system may further include a power supply circuit for providing a power signal and ground to the programmable device, a brown-out circuit for detecting when the power signal drops below a level required to sustain operation of the programmable device, a memory device for recording the number of operating hours of the power train, and software instructions corresponding to the calculation of the number of operating hours of the power train.
It is a feature and an advantage of the present invention to provide a simple and inexpensive combination speed limiter and transmission interlock system which may be retrofit on and/or an option of an engine-transmission power train.
It is another feature and advantage of the present invention to provide a combination speed limiter and transmission interlock system using standard analog and/or digital, off-the-shelf components.
It is another feature and advantage of the present invention to provide a combination speed limiter and transmission interlock system having minimal connections to the coil, the ground and the transmission switch.
It is another feature and advantage of the present invention to provide a combination speed limiter and transmission interlock system requiring less space than that occupied by two separate speed limiter and transmission interlock modules.
It is another feature and advantage of the present invention to provide a combination speed limiter and transmission interlock system that is less expensive to manufacture than two separate speed limiter and transmission interlock modules.
As is apparent from the above, it is an advantage of the invention to provide a combination speed limiter and transmission interlock system. Other features and advantages of the invention will become apparent by consideration of the detailed description and accompanying drawings.